• 전력전자학회논문지
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• 제17권4호
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• pp.337-344
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• 2012

A matrix converter is used for converting AC/AC power directly. In order to generate sinusoidal input/output waveform in matrix converter, it uses nine bidirectional switches and PWM modulation. This paper presents an analytical averaged loss model of matrix converter with DDPWM(direct duty ratio PWM) and proposes a new switching method for reducing switching losses. A Mathematical loss models with average magnitude of voltage/current are classed as conduction and switching loss. The proposed switching pattern is improved with existing DDPWM. To prove improved efficiency with proposed DDPWM, this paper compares losses between suggested switching pattern and conventional switching pattern using mathematical and simulation method. Each loss types are influenced by environmental factors such as temperature, switching frequency, output current and modulation method.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2011년도 전력전자학술대회
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• pp.64-65
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• 2011

The ac power conversion inverter provides the ac power to ECR device for wireless power transfer. In this paper, the operating efficiency of the class-${\Phi}_2$ resonant inverter has been studied through by experiment for optimal design. Its switching frequency is 1MH and the input voltage is 96V which is the output voltage of LLC resonant converter. And its output voltage is 230Vp-p. The efficiency is measured up to 84%.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2008년도 하계종합학술대회
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• pp.537-538
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• 2008

A step-down DC-DC converter with On-chip Compensation for battery-operated portable electronic devices which are designed in 0.18um CMOS standard process. In an effort to improve low load efficiency, this paper proposes the PFM (Pulse Frequency modulation) voltage mode 1MHz switching frequency step-down DC-DC converter with on-chip compensation. Capacitor multiplier method can minimize error amplifier compensation block size by 20%. It allows the compensation block of DC-DC converter be easily integrated on a chip and occupy less layout area. But capacitor multiplier operation reduces DC-DC converter efficiency. As a result, this converter shows maximum efficiency over 87% for the output voltage of 1.8V (input voltage : 3.3V), maximum load current 500mA, and 0.14% output ripple voltage. The total core chip area is $mm^2$.

• Journal of Information Display
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• 제2권4호
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• pp.46-51
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• 2001

Using ray-optics code incorporated with three-dimensional PDP cell simulation, we have analysed the energy flow in the PDP cell from the electric power input to the visible light output. Also, the visible light output profile and viewing angle distribution were obtained. We applied our code to the analysis of the barrier rib height effect on the visible light luminance and efficiency of the sustaining discharge. Although cells with higher barrier rib generate more VUV photons, less ratio of visible photons are emitted toward front panel due to the shadow effect. Thus, there exists optimal barrier rib height giving the highest visible luminance and efficiency. This kind of code can be a powerful tool in designing cell geometry.

• 디지털융복합연구
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• 제17권12호
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• pp.181-190
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• 2019

본 연구의 목적은 중국 전자상거래 기업의 운영 효율성을 평가하고 효율성을 향상시키기 위한 방안을 제시하는 것이다. 본 논문에서는 중국 상무부가 선정한 2017~2018년도 전자상거래 시범기업 중에서 16개 기업을 대상으로 선정하여 전자상거래 기업의 운영 효율성에 대한 실증적 연구를 진행하였다. 투입관점에서 기업의 운영 효율을 측정하기 위해 3개의 입력지표와 2개의 출력지표를 선정하여 데이터포락분석법(DEA)을 활용하여 분석하였다. 분석은 2018년 데이터를 활용한 횡단면 분석과 2016년부터 2018년까지 3년 데이터를 활용하여 종단면 분석을 실시하여 기술효율, 순수기술효율 및 규모효율을 산출하였다. 분석결과 중국 전자상거래 기업의 전반적인 효율성은 지속적으로 향상되고 있으며, 사업 역량과 사업 규모도 점차적으로 향상되고 있음을 알 수 있었다. 본 연구는 전자상거래 시범기업의 운영 효율성 분석을 통해 전자상거래 시범기업의 경쟁력을 평가하고, 운영 효율을 높이기 위한 대책을 제시하였고. 동시에, 규모를 조정하여 경쟁 우위를 강화하기 위한 몇 가지 합리적인 제안을 제시하였다는데 의의가 있다.

• 유통과학연구
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• 제19권7호
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• pp.29-39
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• 2021

Purpose: As China experienced a crisis due to Covid-19, the global supply chain collapsed and affected the world. Therefore, it is time for a change in port operational efficiency, increasing in importance with changes in the global supply chain. This study analyzed Shanghai Port's efficiency, the world's largest port and representative hub port in Northeast Asia, by looking at the relationship between facility factors and cargo throughput to present hub port development's timely implications. Research design, data and methodology: This study applied the Charnes, Cooper, and Rhodes (CCR) and Banker, Chames, and Cooper (BCC) models of the data development analysis (DEA) to construct an analysis from the input-oriented and output-oriented perspectives. Results: As a result, Yidong Container Terminal can be considered the most optimized in facilities and operation processes. Yidong and Shengdong Container Terminal should maintain current operating levels, while Pudong Container Terminal should review facility investments. Also, Zhendong, Huong, Mingdong, and Guandong Container Terminal should be reviewed to increase cargo throughput or to adjust current input variables in the current state. Conclusions: Therefore, the utilization of the container terminal input variables should be reviewed, and the factors of inefficiency should be improved. Moreover, the strategic focus of container terminal operations should be on increasing annual cargo throughput.

• 전기학회논문지
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• 제61권10호
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• pp.1432-1441
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• 2012

In this study, an improved LCCT(Inductor-Capacitor-Capacitor-Trans) Z-source inverter(Improved LCCT ZSI) with characteristics of Quasi Z-source inverter(QZSI) and LCCT Z-source inverter(LCCT ZSI) is proposed. The proposed inverter can also reduce the voltage stress and input current/capacitor voltage ripples compared with conventional LCCT ZSI and Quasi ZSI. A two winding trans in Z-impedance network of the conventional LCCT ZSI is replaced by a three winding trans in the proposed inverter. To verify the validity of the proposed inverter, a DSP controlled hardware was made and PSIM simulation was executed for each method. Comparing the current and voltage ripples of each method under the condition of input DC voltage 70[V] and output AC voltage 76[Vrms], the input current and capacitor voltage ripple factors of the proposed inverter were low as 11[%] and 1.4[%] respectively. And, for generation of the same output AC voltage of each method, voltage stress of the proposed inverter was low as 175[V] under the condition of duty ratio D=0.15. As mentioned above, we could know that the proposed inverter have the characteristics of low voltage stress, low ripple factor and low operation duty ratio compared with the conventional methods. Finally, the efficiency according to load change/duty ratio and the transient state characteristics were discussed.

• 지식경영연구
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• 제22권4호
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• pp.173-187
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• 2021

투입 증대를 통한 경제성장 전략은 급격히 변화하는 경제환경과 맞물리면서 한계를 보이면서 기업의 투입 대비 효율성에 대한 관심이 증가하고 있다. 본 연구는 국내 제조기업 중 연구개발 투자액 상위 938개 기업의 2005~2018년 패널 데이터를 활용하여 기업의 효율성을 측정하고, 효율성에 영향을 주는 요인을 분석하였다. 분석 결과, 기업의 혁신을 위한 투입인 연구개발집중도와 연구개발 성과인 특허가 모두 기업의 효율성을 높이는 것으로 나타났다. 이 밖에 기업의 규모, 부채비율, 수익성 등도 기업의 효율성에 유의미한 영향을 주었다. 분석결과를 통해 본 연구는 기업의 낮은 효율성을 극복하기 위한 지식경영 관점에서의 시사점을 제시하였다.

• 대한전자공학회논문지SD
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• 제49권4호
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• pp.34-42
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• 2012

본 논문에서는 무선전력전송 시스템 수신부의 넓은 입력 범위의 CMOS 다중 모드 정류기를 설계하였다. 다중 모드 정류기의 출력전압을 비교기로 감지하고, 스위치를 컨트롤 하여 정류기 모드를 전환한다. 다중 모드 정류기는 입력 전압의 크기에 따라 자동으로 전파 정류기, 1단 전압 체배기, 2단 전압 체배기로 동작한다. 일반적인 전파 정류기는 10 V에서 20 V까지의 입력 AC 전압에 대해 9 V에서 19 V까지의 출력 DC 전압을 생성할 수 있다. 다중 모드 정류기는 전파 정류기 보다 입력 범위를 5 V 향상시켜서 5 V에서 20 V까지의 입력 AC 전압에 대해 출력 DC 전압은 7.5 V에서 19 V까지 생성되는 것을 보여준다. 다중 모드 정류기의 효율은 전파 정류기 모드에서 94%이다. 제안하는 다중 모드 정류기는 0.35${\mu}m$ BCD 공정으로 설계되었고, 면적은 $2500{\mu}m{\times}1750{\mu}m$ 이다.

• 한국군사과학기술학회지
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• 제11권6호
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• pp.117-126
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• 2008

Recently, the investment and importance have been increasing concerning the researches which are based on fundamental studies. In defense science and technology development, the defense research centers are involved in a large portion of developing the potential capability such as defense applied technology, enhanced human resource, etc. In this paper, we analyzed the relative efficiency of 9 research centers(9 DMU : Decision Making Unit) supported by the defense budget, using DEA(Date Envelopment Analysis) method especially with the CCR-I(Charnes, Cooper, Rhodes-Input) model. Some variables are selected such as budget(input data), patent, article and human resource(output data) to be analyzed. Conclusively, the needs to identify performance-indicators, increase incentives to promote the performance and induce enthusiastic participation in defense science and development projects, are suggested via a relative efficiency analysis.